text: class Emitter:
      def __init__(self):
          self._notifications = []
  
      @property
      def valid(self):
          return len(self.notifications) == 0
  
      @property
      def invalid(self):
          return len(self.notifications) > 0
  
      @property
      def notifications(self):
          return self._notifications
  
      @notifications.setter
      def notifications(self, value):
          return self._notifications.append(value)
  
      @property
      def clear(self):
          self._notifications = []
  